For a few months now, Garmin won’t set a Longest Run record. In the app, the record is blank (shows - - ) and there are no pending records. A couple times a week, my Garmin FR 255 will notify me that I have a new longest run record. But when I go to the activity in Garmin Connect, it doesn’t show as longest run and there is no pending records to approve. This is very annoying.
I had the same issue last year with Garmin not setting a longest swim record. If I recall correctly, the issue did not resolve until I upgraded from my Garmin FR 735xt to the current FR 255.